By Emma Spencer, Science & Technology Reporter

A large Finnish study has found that people taking benzodiazepines and related drugs face a higher risk of dying, with the danger climbing sharply at higher doses.

Researchers from the University of Turku followed 48,124 adults aged 18 to 65 who began using benzodiazepines or Z-drugs in 2006. They tracked them for five years using national health records and compared periods when the drugs were being used against periods when they were not.

Overall, benzodiazepine use was tied to a 28% higher risk of death compared with non-use. The risk was strongly dose-dependent.

• Low-dose use (under 10 mg diazepam equivalent per day) did not raise overall or natural-cause mortality, though it was still linked to higher rates of external causes such as accidents, suicide, and overdose.
• Medium- to high-dose use (10–29 mg) was associated with a 58% increase in all-cause mortality.
• Very high-dose use (30 mg or more) more than doubled the risk of death overall (2.68 times higher). The jumps were especially large for preventable causes: 6.18 times higher for overdose, 4.46 times higher for suicide, and 3.77 times higher for accidents.

Using more than one benzodiazepine at the same time, or combining them with Z-drugs such as Ambien, pushed the risks even higher.

The study, published in Acta Psychiatrica Scandinavica, used a time-varying design that looked at the same people during periods of use and non-use. That approach helps reduce some of the usual confounding, though the authors noted they lacked detailed clinical information on why the drugs were prescribed and could not capture non-prescribed or illegal use.

Benzodiazepines remain widely prescribed for anxiety, insomnia, and related problems. The findings add to a growing body of evidence that higher doses and long-term or multi-drug use carry serious risks that go beyond dependence and withdrawal.

The researchers concluded that the mortality risk is closely tied to dose and that very high-dose use in particular is associated with preventable deaths.